The proposed Phase I study will establish the feasibility of using an innovative, immunoassay-based biosensor for the detection and quatitation of Cryptosporidium oocysts in drinking water. Current method for detection and quantitation of this pathogen frequently are characterized as technically, demanding, time-consuming and labor intense, leading to poor recoveries and false positives and negatives. The propose study will determine the feasibility of using an immunoassay-based biosensor to quantitate the level of Cryptosporidium oocysts present in source and finished waters. The effort will focus on comparing the performance of the biosensor with intact versus extracted oocysts. The goal in Phase I will be to maximize the sensitivity of the assay to detect oocysts. The immunoassay itself should take less than 15 minutes to complete. The availability of more rapid, quantitative methods for detecting water-borne pathogens will help to identify and manage the presence of these organisms for community water supplies, thereby minimizing the exposure of the public. Proposed commercial applications: The proposed biosensor will help address the current deficiency in technology to monitor water-borne pathogens in drinking water. The availability of a rapid, low-cost and quantitative means to test for organisms like Cryptosporidium should help in the effort to minimize exposure for the public to contaminated water.